::
Audio Valve is celebrating the 26h anniversary of the RKV since 1984 ::

Eric - a member of HEAD-FI.COM

About AudioValve RKV mark2, what I can say is that it is a great amplifier that works very well with a very good synergy with electrodynamics Sennheiser HD -600 and HD -800.

It can also be used with Stax headphone (SR- 009) through a Wee box (WooAudio Wee energizer) and Jack Adapter --> Input the Wee HP with using multipliers transformers tension Wee (Ratio: 1:50): very good results, at least as good, see better (in a blind test) compared to the amplifier Stax SRM 727 (best amp Stax currently producing approximately 3 K Euros) and even that amplifier Eddie Current Electra (one 4K dollars amplifier).

You can get an even better sound by shunting the Wee transformers (which retained only for use for the bias voltage generator 580 Volt) for the fifth pin Stax headphone: advantage: its the best ever sound obtained with a Stax SR-009 (best that with the SRM 727 and Electra amp) (sound more transparent, natural and more presence); disadvantage: limited level of between 70 to100 dB (SPL) with listening with headphones Stax SR -009 with sensitivity
at 101
dB / 100 Volts RMS, knowing that the mk2 RKV can get 80 volts RMS for an input of 2.8 volts RMS signal with a very high impedance headphones (145,000 Ohms for the Stax SR- 009).The amplifier will work mainly in voltage, where he excels.

Tube amplifier for
dynamic headphones – preamplifier and power amplifier at the same
time

Up to now the
RKV (tube amplifier for dynamic headphones), developped and admitted
to our distribution in 1982, is by far the most successful tube
amplifier in our product range.

Traditional
Tube technology has been abandoned and replaced by completely unorthodox
approaches to create a concept which is still unique in the amplifier
fabrication. Also it has not been resigned latest semi-conductor
technology and so a product occurred which reflects 40 years of
electronics. The German patent office has secured this idea 1984
with the number DE 3200 51.

“Why headphone
amplifiers” – so the Reader might ask. “Doesn’t my output at the
receiver suffice?” The answer is simply No. Good, dynamic headphones
have a high impedance. For high dynamic jumps, e.g. from CD-Players,
they require much higher voltage levels than the supply voltage
of transistor amplifiers, which would otherwise be a possibility.
The same applies to Hi-Fi systems. So it was one requirement for
the amplifier to bring high levels. Moreover it was important to
achieve short-circuit strenght and excellent technical data, under
the special note of tube sound. The existing concept possesses all
this qualities.

By reason of
the conformation to high terminating impedances the OTL principle
has been appropriated. This concept is geared now to the classic
example of the so-called transformerless power amplifier. With the
help of semi-conductor technology it has proved to be a felicitous
symbiosis of the last 40 years electro-physics.

Also all negative
existing aspects of the tubes, like weathering and tolerance hum,
had to be eliminated. The RKV-electronic manages this problems effortless.
An Op-Amp in the signal path creates a servo circle that compensates
all above mentioned negative characteristics of the tubes.

It is even able to
stabilize the operating point automatically, regardless the weathering
of the tube, so that even older tubes continue working without problems.
This automatic control circuit has no influence on the quality of
the sound, even at the abrasion of the parts.

When judging
the sound especially the high dynamic of the amplifier and the typical
tube sound are to mention.The bass is tight and enormous, the middles
are aery and from a liveley transparency and the high range shows
an excellent release combined with transparent space.

Other products
on the market, which want to force their headphones to diabolic
peaks by the use of smaller battery voltages or 40mWatt output power,
just fail here. Cost-intensive headphones, for example by GRADO
or AKG, require effort and just there the RKV is the only reasonable
driver source.

Of course the
amplifer comes with all this qualities as well in his function as
a pre-amplifer for power amplifiers. In this case the output voltage
of the RKV is decreased to his 15th part and laid on another pair
of Cinch Sockets on the backside of the amplifier.

But there is
even a third way of using the RKV. The performance of nearly 2*3
Watt is also adequate for driving loudspeakers. Therefore we use
the so-called “Impedancer”, that reduces the output impedance of
the RKV to the size of the loudspeakers impdedance. Basically high-class
transmitters which scale down the output voltage. With loudspeakers
starting from 93 dB you can receive an excellent musical result.

The RKV as an
universal genius in this three category groups of Hi-Fi technology
has no competitor that is nearly able to hold a candle to him in
this prize class. For all the people who only consider two of this
mentioned possibilities for their own use the RKV is already the
only right decision.

1) For earphones with impedance lower
than 100 Ohms, use the matching impedance provided by the original
manufacturer. 2) For best sound effects, use high quality earphones.
3) This earphone amplifier brings out the most beautiful and comfortable
sound without distortion. So please properly adjust the volume control
to avoid too loud a volume that may damage your listening pleasure.

On the RKV back panel, there are two sets
of RCA terminals. Why two sets? This is because these two terminal
sets are connected in parallel. When one terminal is used as the
input, the other terminal can then be used for recording output
or connected to the front amplifier. The panel has two earphone
inlets. The manufacturer recommends that simultaneous use of two
low impedance earphones is to be avoided.

I have always had some doubts about the
earphone amplifier: 20 years ago, there was no such thing as an
earphone amplifier. Nor in a recording room I saw the sound man
use such a device. Is it really necessary to buy an earphone amplifier
and discard the traditional earphone equipment? AudioValve does
think the earphone amplifier necessary or it would never be put
into production. The modern audio signal source such as CD has wide
dynamic range which is in fact the voltage range that drives the
earphone. Earphone output from an ordinary amplifier cannot handle
the wide range of voltage variation and hence fail to respond or
give good performance.

USE OF SPECIAL
TUBES

Targeting at the earphone amplifier, the
AudioValve originator Helmut Becker set out his research. What would
be the optimum voltage amplifier element? It is without doubt that
the vacuum tube is the ultimate candidate. What is the limitation
of a vacuum tube? We need to output sufficient current for a low
resistance earphone. The first generation RKV was born in 1984.
Then, the special PCL 805 pentode for TV use was employed. Next,
the RKV Mark II adopted the OTL full vacuum tube differential amplifier
circuit without output transformer. For this special purpose, AudioValve
filed the patent rights of the circuitry (No. DE 3200 517). Helmut
Becker considers this as a breakthrough of the 40 year progress
in audio technology. Using the Op Amp for power supply coupled with
complete vacuum tube amplifier for the signal path provides optimal
combination of the vacuum tube and transistor technology. The circuitry
uses the DC servo Op Amp network for power supply which automatically
adapts to the routing conditions. The manufacturer claims that this
circuitry will function normally throughout the lifetime of the
vacuum tubes.

A BASE FREQUENCY
WITH EVERY DETAIL AND CONTROLLABILITY

We used to give advices on the earphone.
Nonetheless, an earphone can never produce a heart-rending base
energy like a large speaker. Testing an RKV Mark II on Sennheiser
HD-580 (300 Ohm resistance) which I have used for years, I can feel
the base frequency copiously reborn with every characteristic detail
and controllability. The feeling becomes very close to the effect
of a large speaker. Comparing to my Graham Slee Voyager, a portable
earphone amplifier, I can instantly discern the superiority of RKV
Mark II as I can feel a better listening. Where does this better
listening come from? More characteristic details? I quickly switch
between the two earphone amplifiers. I find not much difference
in the characteristic details. But after long listening, I start
to pick up the merit of RKV Mark II as its sound is broader, fuller,
and more stable. There is the characteristic of thickness and relaxation
that makes you feel very comfortable without any pressure. Also,
the sound from the RKV Mark II possesses some warmth and luster
of gold, yet without any antique tube noise. It is the warmth as
well as the luster that brings out the quality of the string instrument.
It provides more elasticity to the guitar sound.

VERY STRONG DRIVE
POWER

If using Beyerdynamic DT 990 Pro (250 Ohms),
the difference becomes more pronounced. For Graham Slee Voyager,
the volume must be turned to the 9 o’clock position to have more
amplification gain and yet the sound drive is still not full enough.
If changed to RKV Mark II, the sound becomes fully open and the
dynamic state and stability are of first class. This brings out
the real value of the flagship earphone device. As to the two low
resistance earphones of AKG K240 Studio (55 Ohms) and Grado SR60
(32 Ohms), the performance can perfectly meet the standard requirement.
But in reference to the earphone amplifier, the difference is not
so obvious. To match the AudioValve with low resistance earphone
(under 100 Ohms), we recommend the use of impedance matching device
with a panel switchable between 8~64 Ohms in four divisions. The
panel also should be provided with a speaker output terminal so
that it can drive high sensitivity speakers. Indeed
the RKV Mark II is quite expensive. However, according to my experience,
a good earphone device can last for a long time and will never be
outdated. Therefore, it is definitely a worthwhile and necessary
investment. The RKV Mark II is absolutely the top choice of all
the earphone devices. I believe that an audio fan should value their
ear highly. Using the RKV Mark II is a royal class enjoyment.

The headphone market is growing. There are exciting new high
end models available. But one thing remains unchanged – STAX headphones are
still one of the most interesting offers in the high end market. STAX is a
strong brand with a long history. And we are convinced also with a bright
future. Many audiophiles regard the SR-007 and SR-009 as the best headphones in
the world.

So what about the amplifier
offerings for STAX headphones? In case of a dynamic or planar headphone you
have the choice, new headphone amps are announced every month. For STAX the
market is different. You can choose the simple way and just order a STAX headphone
amplifier. If you don’t like their sound, you tend to prefer something individual
or look for one headphone amplifier driving your collection of STAX and also dynamic
models the amount of options is very limited. Based on web research you will
find a very few and also very expensive high end especially in the US market –
often without distributors for other regions.

But who is offering a heaven’s gate model which is
affordable and which can be used also for dynamic models? This gap is now
filled by our new electrostatic STAX box called VERTO - design and produced by AudioValve.

Description

The passive box can be used together with AudioValve RKV
II and RKV III tube based headphone amplifiers. There was a simple idea behind
the VERTO. Why not use the transformer in step up mode to produce the high
voltage for the STAX electrostatic headphones? The RKV models use one
transformer per channel (impedancer) to drive low impedance headphones (<
100 Ohm). In the RKV III the transformers are mounted inside the case, for the
RKV II the impedancer can be bought as a separate box. RKV II and III are
regarded to belong to the best sounding headphone amps regardless of price, see
many reviews all over the world.

For a game changing product a simple idea is not enough,
you have to find also a proper implementation. There are already promising
approaches in the market combining transformers with headphone amps to drive STAX
headphones. But RKV and VERTO are now exploiting the full potential of that
approach. Inductance and capacitance of the transformer can harm the sound. The
Pikatron output transformers we use have only very little stray inductances and
capacitances. To avoid distortion we use only a low step up ratio of 1 to 5.
But key is the fact that the output impedances of RKV II and III are extremely
low, too low to cause any negative effect on the sound.

The VERTO supports the current STAX PRO plug with 580 V DC bias as well
as the former bias of 300 V used by older STAX headphones. The higher PRO bias uses
a 5 Pin connector, the 300 V DC bias can be identified by a 6 Pin headphone
plug at the end of the headphone cable. So the VERTO is suitable for all STAX models.

The VERTO has is connected to the
headphone amp with a phone cable and standard plug coming with the VERTO. There
is nothing to buy for you in addition to the VERTO. Also the VERTO does not
require a separate supply voltage. This ensures that there is no interference
and hum caused by main connection. The RKV III has to be switched to the OTL
mode when driving the VERTO.

To increase the versatility we
implemented a switch for 8 ohm as well as 32 ohm. So you can connect high
efficient loudspeakers as well as headphones with low impedance. Feel free to drive
mobile headphones designed for Apple devices as well as low impedance high end planars
like Audeze or Abyss. Check to drive your high efficient
loudspeaker with your tube and transformer based RKV and VERTO chain!

Since the connection of the VERTO to the headphone amp is implemented
via a standard phone plug you can use it also with other headphone amps instead
of the RKV II and III. You will achieve very good results in the case you use a
headphone amp with low output impedance and a high output voltage. We doubt
that you will get to the same ultimate sonic quality as with the RKV models. The
RKV II and III are able to deliver 100 volts peak-peak drive.

We use only high quality
components in the box. The Picatron transformers are built based on our
specifications. For wiring the main audio connections to the sockets of the headphones and the STAX female socket cable we use a well-known German high end audio cable manufacturer by the name of HB cable design from Cologne. The core of the cable is made of silver-plated oxygen-free copper conductors stranded several times.

- Two Combi jackets phone plug
and XLR for dynamic and planar headphones

- Loudspeaker terminals to
connect spades or bananas

- 60 cm cable with phone plug
fixed to the case for connection to the headphone amp (like Audio Valve RKV II
and III as well as other headphone amps with low output impedance and high
output voltage)

- No separate supply voltage
needed, static high voltage is generated by the signal

- One high quality Pikatron
output galvanic coupled transformer for each channel

- Internal bias voltage for
STAX 300 + 580 VDC (LED controlled)

- Internal HB cable design with a cross section of 0.72 sq. mm, embedded in a PTFE Teflon insulation air. The conclusion is a 5 mm diameter strong silicon of insulation, the high-voltage signal line outwards reliable and well insulated

- The device provides both the
required for the operation of the headphone-static voltage of 300 / 580 VDC,
and up to 550 Vrms signal voltage

- Bandwidth up
to nearly 100 KHz - ( 470 pf load )

- Dimensions: w * h * d ( cm ) - 110 * 105 * 165

- weight: 2 kg

Options:

- Silver case (black on
request)

- Chrome mode switch (golden
on request)

- Cable with phone plug 60cm
length (different length on request)

- Price: 690,- EUR including VAT

pic 1 -

show you the excellenttransmission propertiesof theVERTO used on aSTAXheadphoneconnected to theoutputof the
RKV Mark 2 as driver.

pic 2 -

show you a triangle signal by 10 kHz

pic 3 -

when you support the speaker terminals in reverse mode from any transistor amp, you can supported STAX headphones too.

1) For earphones with impedance lower than 100 Ohms, use
the matching impedance provided by the original manufacturer. 2) For best sound
effects, use high quality earphones. 3) This earphone amplifier brings out the
most beautiful and comfortable sound without distortion. So please properly
adjust the volume control to avoid too loud a volume that may damage your
listening pleasure.

On the RKV back panel,
there are two sets of RCA terminals. Why two sets? This is because these two
terminal sets are connected in parallel. When one terminal is used as the
input, the other terminal can then be used for recording output or connected to
the front amplifier. The panel has two earphone inlets. The manufacturer
recommends that simultaneous use of two low impedance earphones is to be
avoided.

I have always had some
doubts about the earphone amplifier: 20 years ago, there was no such thing as
an earphone amplifier. Nor in a recording room I saw the sound man use such a
device. Is it really necessary to buy an earphone amplifier and discard the
traditional earphone equipment? AudioValve does think the earphone amplifier
necessary or it would never be put into production. The modern audio signal source
such as CD has wide dynamic range which is in fact the voltage range that drives
the earphone. Earphone output from an ordinary amplifier cannot handle the wide
range of voltage variation and hence fail to respond or give good performance.

USE OF SPECIAL TUBES

Targeting at the earphone amplifier, the
AudioValve originator Helmut Becker set out his research. What would be the
optimum voltage amplifier element? It is without doubt that the vacuum tube is
the ultimate candidate. What is the limitation of a vacuum tube? We need to
output sufficient current for a low resistance earphone. The first generation
RKV was born in 1984. Then, the special PCL 805 pentode for TV use was
employed.

Next, the RKV Mark II adopted the OTL full
vacuum tube differential amplifier circuit without output transformer. For this
special purpose, AudioValve filed the patent rights of the circuitry (No. DE
3200 517). Helmut Becker considers this as a breakthrough of the 40 year
progress in audio technology. Using the Op Amp for power supply coupled with
complete vacuum tube amplifier for the signal path provides optimal combination
of the vacuum tube and transistor technology. The circuitry uses the DC servo
Op Amp network for power supply which automatically adapts to the routing
conditions. The manufacturer claims that this circuitry will function normally
throughout the lifetime of the vacuum tubes.

A BASE FREQUENCY WITH EVERY DETAIL AND CONTROLLABILITY

We used to give advices on the earphone.
Nonetheless, an earphone can never produce a heart-rending base energy like a
large speaker. Testing an RKV Mark II on Sennheiser HD-580 (300 Ohm resistance)
which I have used for years, I can feel the base frequency copiously reborn
with every characteristic detail and controllability. The feeling becomes very
close to the effect of a large speaker. Comparing to my Graham Slee Voyager, a
portable earphone amplifier, I can instantly discern the superiority of RKV
Mark II as I can feel a better listening. Where does this better listening come
from? More characteristic details? I quickly switch between the two earphone
amplifiers. I find not much difference in the characteristic details. But after
long listening, I start to pick up the merit of RKV Mark II as its sound is
broader, fuller, and more stable. There is the characteristic of thickness and
relaxation that makes you feel very comfortable without any pressure. Also, the
sound from the RKV Mark II possesses some warmth and luster of gold, yet
without any antique tube noise. It is the warmth as well as the luster that
brings out the quality of the string instrument. It provides more elasticity to
the guitar sound.

VERY STRONG DRIVE POWER

If using Beyerdynamic DT 990 Pro (250 Ohms),
the difference becomes more pronounced. For Graham Slee Voyager, the volume
must be turned to the 9 o’clock position to have more amplification gain and
yet the sound drive is still not full enough. If changed to RKV Mark II, the
sound becomes fully open and the dynamic state and stability are of first
class. This brings out the real value of the flagship earphone device. As to
the two low resistance earphones of AKG K240 Studio (55 Ohms) and Grado SR60
(32 Ohms), the performance can perfectly meet the standard requirement. But in
reference to the earphone amplifier, the difference is not so obvious. To match
the AudioValve with low resistance earphone (under 100 Ohms), we recommend the
use of impedance matching device with a panel switchable between 8~64 Ohms in
four divisions. The panel also should be provided with a speaker output
terminal so that it can drive high sensitivity speakers.

Indeed the RKV Mark II is quite expensive.
However, according to my experience, a good earphone device can last for a long
time and will never be outdated. Therefore, it is definitely a worthwhile and
necessary investment. The RKV Mark II is absolutely the top choice of all the
earphone devices. I believe that an audio fan should value their ear highly.
Using the RKV Mark II is a royal class enjoyment.

New fashion of headphones—new fascinating headphones of this month

Overall drive! Another classic of tube-transistor hybrid amplifier

By Lin Jialiang

In the global spectrum of acoustics, “Made in Germany” always symbolizes preciseness and extreme high standards while its sound aesthetics represents a style of order, balance, strength, powerful action, self-restraint expression, decisive attitude and heroic spirit. (To illustrate with a pianist, Wilhelm Backhaus will be the very representation.) Besides, there is a major feature shared by the traditional German acoustics due to the
consonants in German,
whether being voiced, voiceless or even double consonants, they will always be produced clearly with powerfully cadence, which has virtually shaped the majestic and powerful style of German acoustics as well as the detailed and clear end sounds.

All those features mentioned above can be found in the brass brands such as T+A and Burmester as well as small brands such as MBL and Audio Valve. Noticeably, the German Sound based on the nationality tends to be more evident at small German brands and this is because the brass brand acoustics will adjust to local tastes according to aesthetic standards of different areas during the process of globalization. While the small brands are
free from such
problems and can do better in upholding its own style, and therefore it is more common to hear sounds from ASR and Audio Valve with strong German flavor.

Acryl cover—good in promoting music performance

Audio Valve is owned by Helmut Becker, whom I neither know nor meet in person. And I even don’t know how he entered this industry of acoustics. However, based on limited information from the English world, with a particular and strict taste, he will do everything himself. He won’t stop midway unless he has developed the product to the best, or publish the key techniques unless he has obtained patent rights. You can search for Helmut
Becker’s life story
on the internet. Otherwise, you can catch a glimpse of his personal style from the Audio Valve products because “You are What You Create”.

With a distant view, people will tend to associate RKV MK2 with its sister product MBL due to the black framework and golden knobs, and also connect it with another small yet refined brand: ASR, because of its acryl cover, which is as thick as 1cm. As far as the overall view is concerned, RKV MK2 impresses people with its majestic and magnificent style peculiar to German.

However, why the acryl cover? According to the study of material and sound, the acryl plate is smooth, gentle, soft and flexible with good music performance. It can also filter tiny details and noise in acoustics. Metal materials, which increase details, linearity yet with a sharp and hard tone, and the acryl plate are mutually complementary. And the proportion of mixture will indicate the ability of sound tuning of each manufacturer.
Since Helmut Becker,
who is famous for his particular taste, applies the design of acryl cover, it will definitely show his tuning skills.

[Text to picture one:

It is easy to associate RKV MK2 with its MBL due to the black framework and golden knobs, and also connect it with another small yet refined brand: ASR, because of its acryl cover, which is as thick as 1cm. As far as the overall appearance is concerned, RKV MK2 impresses us with its majestic and magnificent style peculiar to German. ]

As to the music performance, I will talk about it later as I share my personal view about RVK MK2. What we know for sure in the least is that, the manufacturer who applies the acryl cover must be very proud of its circuits subconsciously, and don’t worry about the plagiary problems (after all the product is protected by patent rights) and tests by experts. Therefore, what is special about the circuit design of RVK MK2? Its amplification
circuit applies
the structure of OTL zero-output transformer and double single-track vacuum-tube differential amplification. Designed in this way, basically, vacuum tubes take the full control of the output of amplifier. In other words, Helmut Becker is very confident of the performance of vacuum tubes. What kind of tubes does RKV MK2 apply? They are PCL 805 (18GV8) of Elektronska Industrija (EI), which used to be applied as the five-stage tube on TV set. Frankly speaking, except RKV MK2, I can’t remember of any amplifier manufacturer,
which has ever applied this kind of tube for amplification. With these rare tubes, Helmut Becker shows qualities and specialities, which will be testified soon later.

I'd like to remind you of its signal amplification circuit, which connects the Operation amplifier as DC server with four Ei PCL 805 tubes, and many ICs and active/passive units placed nearby for the purpose of bias regulation, which comprises the special design of bias regulation for vacuum-tube amplifiers. And this famous patent of ABR (Automatic Bias Regulation) of Audio Valve will not only integrate qualities of transistors and tubes,
supply a maximum
output voltage of 80V, a high voltage output of 3 W (100-400?) for each track, and the standard impedance factor as high as 3600, which is enough to drive any kinds of headphones with various impedances and voltages (the manufacturer states that the headphones can range from 32 to 2000 on its website), but also automatically adjust the output power of each tube according to its working conditions so as to minimize their effects on the performance of RKV MK2. Then, even it becomes necessary to replace tubes, replacing
one tube is enough for one time and the tube matching and complete replacements are not necessary. To sum up, ABR is definitely helpful with stabilizing the performance and extending the lifespan of tubes. By the way, the former version of RKV Mark II, the so-called second version, was designed in 1982 to celebrate the 25th anniversary of the brand.

Need warming up like good wine

In the formal test, I applied the USB DAC digital current Onix DAC25A as signal source, Furutech GT2 as leads, and windows 7 + Foobar2000 + WASAPI as playing software, and the control group consists of DA&T HA-1A and Kingrex HQ-1, and as to the headphones for reference, I have tried AKG K701, Sennheiser HD800, Grado RS-1 and Denon AH-D7000, with various test results, among which AKG K701 did the best on the whole because it didn’t
change the original
characteristics and brand features of headphone (I think this point is of special importance to the fundamentalists of headphones), and therefore, all the following opinion comes from the arrangement of RKV Mark II with K701.

[Text to picture

This equipment has two sets of RCA input jacks and no pre-amp switch, which make it convenient for the users to input two signal sources. ]

[Text to picture

The ABR (Automatic Bias Regulation) that makes the manufacturer feel proudest is also applied, which has made use of the tube-transistor hybrid circuit to the best. ]

Within half an hour after turning on, RKV Mark II played extremely comfortable music, soft and smooth in tone, with a strong flavor special to tube amplifiers; however, something was missing in its music quality, and that was like the wine, which had not been decanted and therefore tasted a little acerb, was short of sweet aftertaste. However, after half an hour of warming up, its performance was totally different. It activated its full
potentials so
that the weak point of being loose and short of power at bass frequencies was fully recovered, and the bass sound became more condensed, powerful, and flexible and clearer, which continued smoothly with clear arrangements, grain and rich scales. What’s more fascinating is that the musical cadence was taken fully under control when RKV Mark II was used to drive K701, which was quite difficult to see in tube-structured amplifiers.

Who can say no to such powerful and clear bass frequency quality? It was not only K701 that could make such fascinating chemical transformations; however, when RKV Mark II was connected with HD800, which performed unsatisfactorily at bass frequencies, or other headphones, the performances at bass frequencies were all improved. The differences just lied in how better for each headphone or, with the bass frequency being improved, whether
it could harmoniously
join in with tweeter frequencies. Obviously, with RKV Mark II as the drive, as far as musical qualities such as tone, density, speedy and resolution were concerned, the tweeter and bass frequencies of K701 joined in more closely and smoothly; while playing human voice, the midrange frequencies could improve the resonance within the singer’s chest and the eruption as well as the sturdy linearity (fleshliness), which made the music sound stronger, vivid and dynamic. In addition to the warm treble, it also could
filter noise, embellish the music, and make necessary compression to avoid Peak break, and with all these together, human voice sounded more vivid, emotional and touching.

Both improvements of depth of bass frequencies and width of sound field

Warm, strong, clear, pure, soft, comfortable, pressureless, low base noise and high resolution were the key points I constantly wrote down when I listened to different headphones such as K701 that were driven by RKV Mark II, and only when K701 was connected with it, could I put down so many advantages (certainly with the most notes). Furthermore, as we known, K701, which lacks in base sound, is a kind of headphone with strong temperament,
which will
be lost as most amplifiers try to power it up; if the temperament of headphone is fully taken care of, it is usually unavoidable to limit the types of music that K701 can play. Back to RKV Mark II, it will not only bestow K701 with powerful momentum, but also reserve its original refined temperament. Sorry, I shall say it becomes better.

Finally, there were improved results as RKV Mark II was connected with various headphones, and it was because it extended the depth of the sound field and at the same time strengthened impression of being surrounded by sound. Take the arrangement with K701 as example, the open-designed K701 could not create such vast found field as that of HD800 and HD650, which could be described as open and natural (especially natural). Driven by RKV
Mark II, the
sound field, compared with the control group, became deeper and broader with clearer resolution as well as clearer arrangement and position. What’s more surprising was that the sound image was created right before one’s eyes instead of his head, and its sound field could cross over the upper limit of “180 Degree Line of Headphones”—Joan Baez’s Diamonds and Rust in the Bullring. Listening to this album, the cheer and applause of the audience on the back were also reproduced vividly making a live impression of
“as one falls, another rises”. It could be found that this amplifier did quite well in reproducing details and vividness in open space.

Among the best

To sum up, although my personal idea is that the arrangement of RKV Mark II with K701 is the best, I believe that it is highly possible for fans of other headphones to love this vacuum-tube amplifier. After all, warm and mellow tone, strong linearity, rich flavor of analogy, touching impression, and excellent music quality are advantages many amplifiers can never have. As far as the acoustic quality is concerned, the vacuum-tube structure
of RKV Mark
II is almost immune to the influence of impedance of different headphones. With high voltage output, it can easily drive any headphones and reproduce the record’s dynamics. Furthermore, the performance of RKV Mark II in clarity, speed and resolution are among the top rank in the vacuum-tube amplifier spectrum. Its performances when arranged with various headphones are beyond the standard with the difference being: whether the headphone itself can withstand such powerful drive. Therefore, although I am not sure
whether the fundamentalists of headphones will like the sound qualities of RKV Mark II, I am sure that RKV mark II is among the best amplifiers that I’ve listened to! (Dean Lin Audio Company Ltd.: 03-2127378)

[Text to picture

A patent right has been obtained for the special vacuum amplification circuit designed by Helmut Becker for RKV MK2. ]

Test results

Figure 1 is the FFT frequency spectrum graph of this equipment with 1 KHz sine wave signal, a load of 200? and an output of 10mW and it is clear that the second-harmonic generation is about 100pW, and the 60Hz harmonic is also 100pW with a THD+N reading as 0.015%; Figure 2 is the FFT frequency spectrum graph of this equipment with 1 KHz signal, a load of 200? and an output of 100mW and it is clear that the second-harmonic generation
is about 100nW with
a THD+N reading as 0.015%; Figure 3 is the frequency response of 1mW, 10mW, 100mW and 1W, and it's clear that the high frequency can extend to 80 KHz (-3dB). Figure 4 is the coordinate graph of output to distortion, and it is clear that the signal harmonic begins to increase with an output above 50mW and the maximum power without cutting wave shape is 4.4W. (Guan Peiqing)

On each boardisthe model nameof the productandthe name of thetubesisset.So if youare not surewhichtubeyou need,pleaselook at thecircuit boardandwatchwhat
is writtenthere(PCL805-orECL85(6F5P)In mid-2015has
been changed fromPCL805onECL85that
affects themodelsRKVall,LuminareandSolaris

Thewarranty is
void ifthe top glassof the
amplifieris takenwithin
the warranty period. Alsovoid the warranty, if
otherthanthat we
offertubes are usedforthe so-called"tuberolling". To buynew tubes, please
contact your dealer, he has recommendedtubes on
stock. IncidentallyTube Rollingis simplystupidin the modelsRKV, LuminareandSolaris. You canconvince yourselfbyknocking on thetubes,
they willnot hear anyknocking soundsin the headphones.

Technical explanations for RKV2 and LUMINARE that show whythis conceptprovidessuch goodresults

The following photo showsyou ascreenshotfrom theoscilloscopefrom a channelonRKV2-Model20166F5Pwith attachedVertoand8ohm loadat the output.You see, thisclearlyrepresents thenewmodelseriesmorepower at the outputat your disposal,asthepasthas been the case.There-sizingof some componentsandsmallcircuitcorrectionsdelivertodayonRKV2inOTLmodeatthe beginningofSoft Clippingper channel8watts.

The following photo showsyou ascreenshotfrom theoscilloscopefrom a channelonRKV2-Model20166F5Pwith attachedVertoat
the outputof theSTAXsocket.Due to the increasedpower of theRKV2the yieldofSTAXsignalnow arisesvoltageisatVertofollowingmeasures.